Re: [ctypes-users] Iterate over poiters - Newbie

[Thomas H. <th...@py...>]

Michele Petrazzo <mic...@un...> writes:

> I'm not a C/C++ developer, so when I use ctypes with pointer and other
> hard (for me) C "magic" things, I find some problems.
>
> My problem, like you can see into this "long" code, is how to translate
> the "magic" iteration over a pointer ( pal[i] ) into a python code.
>
> P.s. I'm go crazy with this. Please help me... :)
>
...
>
>   def go(self):
>    pal, point = self.GetPalette(bitmap)
>    r,g,b = pal
>    colUse = self.GetColorsUsed(bitmap)
>    ##### <--- Here is my problem, I cannot iterate over point.contents!
>    for i in range(colUse):
>     cont = point.contents
>     cont.rgbRed    = 255 - r
>     cont.rgbGreen = 255 - g
>     cont.rgbBlue  = 255 - b

You must not use the .contents attribute to access the contents of a
ctypes pointer.  Use indexing, just as you would in C:

   def go(self):
    pal, point = self.GetPalette(bitmap)
    r,g,b = pal
    colUse = self.GetColorsUsed(bitmap)
    for i in range(colUse):
     cont = point[i]
#                ^^^
     cont.rgbRed    = 255 - r
     cont.rgbGreen = 255 - g
     cont.rgbBlue  = 255 - b

Does the tutorial talk about .contents?  Then it should be fixed.

Thomas